The present invention relates to environmentally degradable articles, films, bags together with containers fabricated from the degradable polymeric compositions.
A wide variety of environmentally degradable polymeric compositions have been used for the fabrication of containers, article carriers, films, bags and the like in the past. Many of these polymeric compositions required the use of photosensitive additives to a host polymer to impart environmental degradability to the articles, particularly by photodegradation mechanisms. The use of such additive systems have caused substantial problems in the past. For example, such polymer-photosensitive additive systems have exhibited spontaneous separation of the components or component migration to surface of the article during and after melt extrusion. Further, such additive systems are often subject to discoloration or odor generation during processing of the melt. This requires the addition of dye colorants to maintain an acceptable product appearance. Further, such systems have had poor extrusion viscosity characteristics and poor thermoformability and have not exhibited the requisite stiffness or flexibility for certain applications.
Article carriers for bottles comprise rigid carriers capable to snap-fit engagement with the neck finish portion of filled bottles. Such rigid carriers usually include a downwardly depending sidewall portion attached to a centrally located top panel, which sidewall portions engage the shoulder portions of the containers held within the carrier. The top panel includes a plurality of bottle neck engaging portions which hold the neck finishes of the containers in a predetermined geometric array. Rigid carriers are usually fabricated from a melt extrudable polymer which can subsequently be thermoformed into irregular geometric shapes. The material must also have the required stiffness to hold the container necks within the carrier and still have degradability on environmental exposure after its normal service life.
Rigid carriers are usually formed from an extruded blank and the final shape thermoformed from the blank into individual carriers. In addition to the extrudability and thermoforming properties, the material must include adequate stiffness characteristics for retaining heavy, filled containers during transportation, storage and use. Also, the material must have sufficient balanced degradability characteristics such that it degrades under normal environmental conditions rapidly enough to dissipate in the environment, yet slowly enough that it will not degrade during normal shelf life, storage or shipment time periods. Such premature degradation would affect the strength of the carrier, and thus the structural integrity of the rigid carrier thereby diminishing its container retentive capability. Further, the material used for the rigid carriers must resist migration or separation of the various components of the material during melt processing and normal use.
In the past, a blended material of high density polyethylene or medium density polyethylene admixed with an ethylene-carbon monoxide copolymer in the concentrations of 3-50 percent ethylene-carbon monoxide copolymer, wherein the mixture contains about 0.1 to about 15 weight percent of carbon monoxide has been used for various articles. Such a degradable polyethylene ethylene-carbon monoxide copolymer material is described in German Patent document No. 2316697 entitled "Polymeric Substance Photo-Decomposable By the Action of Ultraviolet Irradiation."
The material disclosed in German patent document No. 2316697 is limited to high density polyethylene and medium density polyethylene having between 3-50 percent ethylene-carbon monoxide copolymer and discloses the use of copolymers of ethylene-propylene, ethylene-butene, ethylene-vinylacetate, ethylene-styrene, ethylene-methylacrylate and ethylene-hexene copolymers in the place of polyethylene. The polyethylene-ethylene-carbon monoxide blended materials disclosed in the No. 2316697 document degrades too rapidly for successful use as rigid article carriers and do not have the mechanical properties required for rigid article carriers. Accordingly, there exists a need in the art for an environmentally degradable polymeric composition having sufficient mechanical properties for use as an article carrier for filled containers, which exhibits balanced environmental degradation, excellent mechanical properties, extrudability, thermoformability and does not spontaneously suffer component migration or separation upon melt extrusion formation or during use.